Waterproof breathable fabric laminates and method for producing same

ABSTRACT

Disclosed herein are polyurethane compositions specifically adapted to produce non-porous membranes exhibiting waterproof and water vapor transmissible charactertistics. The membranes can be produced as free standing products or can be produced as coatings on porous substrates to confer similar properties to such substrates. Also disclosed are coated fabrics and fabric laminates utilizing the membranous coatings of the invention and exhibiting waterproof and water vapor transmissible characteristics. Such coated fabrics and fabric laminates find utility in the fabrication of tenting, rainwear and other garments where waterproofness, coupled with breathability, are important features.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of co-pending application Ser. No.07/914,871, filed Jul. 16, 1992.

FIELD OF THE INVENTION

The present invention relates generally to waterproof breathablepolyurethane membranes, to a coating method and system for producingsame on porous substrates and to waterproof breathable poroussubstrates, particularly fabrics, comprising such membranes.

BACKGROUND OF THE INVENTION

A well known waterproof breathable textile laminate of commerce, soldunder the brandname, GORE-TEX, is technically based upon the use of amembrane of hydrophobic, microporous, expanded polytetrafluoroethylene(hereinafter "PTFE") as an essential functional component thereof. Formost purposes, the microporous PTFE membrane of the laminate issandwiched between inner and outer fabric layers, the membranegenerally, although not necessarily, being continuously bonded and/oradhered to one or both fabric layers. Such hydrophobic microporous PTFEmembranes and the preparation thereof are described in U.S. Pat. No.3,953,566, Robert W. Gore, issued Apr. 27, 1976 and U.S. Pat. No.4,187,390, Robert W. Gore, issued Feb. 8, 1980. The preparative methodbroadly comprises the uniaxial or biaxial stretching of an unsinteredhighly crystalline PTFE sheet, prepared by paste extrusion, at a rateexceeding 10% per second while maintaining the temperature thereof atbetween about 35° C. and the crystalline melt point of the polymer. Theresulting membranous PTFE product of this process has a microstructurecharacterized by nodes interconnected by fibrils and is possessed of aninteresting and useful combination of properties which befits it for usein the preparation of waterproof breathable textile systems. Morespecifically, the hydrophobic, microporous, expanded PTFE membranes ofthe above Gore patents are sufficiently hydrophobic and the microporessmall enough such that the membrane can function as a barrier to thepassage of bulk water therethrough at significant hydrostatic pressures.On the other hand, due to the microporous character thereof, saidmembranes also possess the capacity to allow diffusion of water vaportherethrough. Thus, these desirable properties of waterproofness andwater vapor transmissibility or "breathability" are imparted to textilelaminates in which such a membrane comprises a component layer.

Despite its relative success in the marketplace, the waterproofbreathable textile laminate systems based on the hydrophobic microporousexpanded PTFE membrane of the above-identified Gore patents are,nevertheless, possessed of certain deficiencies. Firstly, such expandedPTFE membranes are relatively expensive. Secondly, because waterproofbreathable textile laminates utilizing such microporous expanded PTFEmembranes are necessarily constructed by some form of physicallamination of the previously prepared PTFE membrane to at least onepreviously prepared fabric layer, equipment and operative techniquesmust be provided to handle the membrane and the fabric, to properlyindex them and to secure the PTFE membrane layer to the fabric layer.Thus, the techniques used to prepare such laminates are generallysubstantially more complex, arduous and expensive as compared toconventional liquid coating and curing techniques known in the fabriccoating art. Thirdly, PTFE materials are generally known to be ofadhesion resistant character. Therefore, where it is desired to preparea waterproof breathable textile laminate by means of a continuousbonding of the PTFE membrane layer to a fabric layer, such as byinterposition of a continuous adhesive layer between the microporousexpanded PTFE membrane layer and the fabric layer, the resulting bondstrength, albeit usually adequate, is generally relatively low and theselection of a suitable adhesive which can accomplish the necessarybonding without substantial adverse affect upon the breathability of thesystem can be a problem. Another problem associated with the use of themicroporous expanded PTFE membranes in textile laminate systems residesin the finding that such membranes, over a period of use, can cracksufficiently as to provide sites for bulk water leakage or seepagetherethrough. Apparently, the many micropores necessarily embodied inthe polymer matrix can act as crack propogation loci and this, coupledwith the crystalline nature of the polymer, result in a membrane whoseflexure life is somewhat limited. Finally, the expanded microporousmembranes of the above-identified Gore patent are apparently susceptibleto significant loss of their waterproof characteristics when contactedwith such surface active agents as are inherently contained in humanperspiration. Obviously, this can be a serious detriment where textilelaminates employing these membranes are employed as garment materials.This problem, as well as a solution therefor, is disclosed in U.S. Pat.No. 4,194,041, Gore et al., issued Mar. 18, 1980. The solution thereindisclosed resides in the interposition of a continuous, hydrophilic,water vapor transmissible layer between the microporous hydrophobicmembrane surface and the surfactant source. Thus, with respect togarments fabricated with a waterproof breathable textile laminateprepared in accordance with the aforementioned Gore et al patent, themicroporous hydrophobic membrane layer faces the exterior of the garmentwhile the continuous hydrophilic layer faces the interior of thegarment. In this role, the continuous hydrophilic layer functions as abarrier to the surfactant contaminants in human perspiration andprevents contact thereof with the hydrophobic microporous PTFE membrane,thereby to preserve the waterproof character of the membrane. Asdisclosed, the continuous hydrophilic layer of the construction can bein the nature of a hydrophilic polyurethane based on a reactivecrosslinkable prepolymer having an isocyanate terminated branchedpolyoxyethylene backbone. Attachment of the continuous hydrophilic layerto the microporous hydrophobic membrane can be discontinuous, such as inthe nature of sewing or adhering together of the edges of the respectivelayers by thread or adhesive. The use of a continuous adhesive bondbetween the hydrophobic and hydrophilic layers is apparently believed bythe patentees to be potentially detrimental to the water vaportransmission properties of the laminate and so is not discussed ordisclosed. Where continuous bonding of the respective layers of thelaminate is desired, patentees disclose a technique whereby directbonding of the one layer to the other is achieved. Said techniqueinvolves the casting of the hydrophilic layer directly onto the surfaceof the microporous hydrophobic membrane layer with application ofsufficient hydraulic pressure as to force the hydrophilic layer into thesurface voids of the hydrophobic layer. Thus, while the Gore et al.patent may provide a second generation solution for the surfactantcontamination problem disclosed to exist with respect to garmentapplications involving the first generation hydrophobic microporousexpanded PTFE membranes disclosed in U.S. Pat. Nos. 3,953,566 and4,187,390, it is obvious that the solution is achieved at the expense ofadded complexity and, of course, cost.

In U.S. Pat. No. 4,532,316, Robert L. Henn, issued Jul. 30, 1985, thereis generally disclosed a phase separateed polyurethane prepolymer havinghard and soft segments and elastomers prepared therewith. The prepolymercomprises the product of reaction of (a) a polyol having a numberaverage molecular weight of between 600 and 3500, (b) a polyisocyanatehaving a functionality of at least 2, and (c) a chain extender having amolecular weight of no greater than 500, these components of theprepolymer being present within a specified range of proportions. It isfurther disclosed that, where the polyol component employed ispoly(oxyethylene) glycol, the prepolymer can be formed into cured filmshaving superior moisture vapor transmission properties and that suchprepolymer can thus be formed as a composite with various textiles foruse in rain protective garments. Example 10 of the patent discloses thepreparation of breathable coated textiles by melt coating of a fabricwith poly(oxyethylene) glycol based prepolymers prepared in accordancewith the invention followed by moisture curing of the coating. Saidbreathable coated textiles were found to be durably waterproof underscoring and flexing tests and were stated by patentee as being suitablefor use in rain protective wear. In Example 11, a hydrophilic phaseseparated non-porous film of hydrophilic polyurethane was directlybonded to an expanded PTFE membrane in the manner of the aforementionedU.S. Pat. No. 4,194,041. A poly(oxyethylene) glycol based prepolymerdifferent from those employed in Example 10 was utilized and roll coatedonto the PTFE membrane under pressure, followed by ambient moisturecuring of the coating. The resulting PTFE/polyurethane composite wasdiscontinuously adhered to a textile fabric to form a breathable textilelaminate, the PTFE layer being being sandwiched between the fabric andpolyurethane layers. The patentee discloses this textile construction asbeing suitable for the fabrication of excellent rain protective weartherefrom. From the disclosure it is suggested that Henn regards theattainment of acceptable moisture vapor transmissions rate for clothingpurposes as being absolutely dependent upon the use of apoly(oxyethylene) glycol based prepolymer and, to a lesser extent, uponthe extent of phase separation attained between the hard and softsegments of the cured polymer.

In accordance with the present invention there is provided a waterproofbreathable polyurethane membrane whose waterproofness and breathabilityproperties are not dependent upon the presence of microporosity and inwhich at least several of the problems related to the known microporousmembranes of the prior art have been solved or substantiallyameliorated. In another aspect of the invention, the polyurethanemembranes hereof are disposed over porous substrates, particularly ascoatings applied to fabrics, thereby to confer waterproofness andbreathability to such substrates.

OBJECTS OF THE INVENTION

It is a principal object of the invention to provide a novelpolyurethane composition which, in non-porous membranous form, iswaterproof and water vapor transmissible.

It is another object of the invention to provide a novel non-porouspolyurethane membrane which is waterproof and water vapor transmissible.

It is another object of the invention to provide the novel non-porous,waterproof and water vapor transmissible polyurethane membrane hereof inthe form of an adherent coating.

It is another object of the invention to provide porous materialsubstrates to which waterproof and water vapor transmissive propertieshave been conferred by disposition of the polyurethane membrane of theinvention thereover.

It is still another object of the invention to provide a novelwaterproof and water vapor transmissible coated fabric.

It is another object of the invention to provide a novel waterproof andwater vapor transmissible textile laminate construction.

It is yet another object of the invention to provide a novel solventbased polyurethane coating system whereby porous material substrates,such as fabrics, may be rendered waterproof and water vaportransmissible by conventional coating techniques.

Other objects and advantages of the present invention will in part beobvious and will in part appear hereinafter.

SUMMARY OF THE INVENTION

The polyurethane membrane of the invention is a cured polyurethane filmarising as a reaction product of: (a) an organic polyisocyanate, (b) apolyalkylene ether glycol wherein the number of carbon atoms of thealkylene radical is 2, in other words a poly(oxyethylene) glycol, (c) atleast one polyalkylene ether glycol wherein the number of carbon atomsdefining the alkylene radical is at least 3, and (d) a reactive hydroxygroup-containing polydimethylsiloxane having a functionality of at least2. The mole ratio of the polyalkylene ether glycol of (a) to thepolyalkylene ether glycol of (b) can be within the range of 1.5:0.5 to0.5:1.5. The mole ratio of the reactive polydimethylsiloxane of (d) tothe total glycols of (b) and (c) can be within the range of 0.1:1 toabout 0.3:1. The polyurethane composition can be prepared utilizing thewell known prepolymer or one-shot routes although, in applicant's beliefthe prepolymer route is more versatile and is, therefore, preferred.Utilizing the prepolymer route, a single NCO- terminated prepolymer canbe prepared bearing the compositional requirements set forth above andthen chain extended to provide a curable composition suitable forpreparation of the cured membrane of the invention. Alternatively, twoNCO- terminated prepolymers can be separately prepared, each prepolymerchain extended and the chain extended prepolymers blended in theappropriate amounts prior to or during formation of the membrane andprior to curing thereof. Using this scheme the first prepolymer isformed from the polyethylene glycol and reactive hydroxylgroup-containing polydimethylsiloxane to form an isocyanate terminatedrandom block urethane copolymer of polyethylene oxide andpolydimethylsiloxane. The second prepolymer is performed from thepolyoxyalkylene glycol(s) of (c). Each of these prepolymers is chainextended in the conventional manner, utilizing low molecular weightchain extenders having terminal labile hydrogen atoms. These chainextended prepolymers may then be suitably blended in the amountsrequired to bring the blended composition within the foregoingcombination of compositional parameters prior to or during formation ofthe membrane and at any time prior to curing thereof. A particularlyflexible system for accomplishing the blending of the chain extendedprepolymers resides in preparing separate solutions thereof in inertfugitive solvents, coating the surface of a porous substrate desired tobe rendered waterproof with the first (block copolymer) extendedprepolymer solution and driving off the solvent therefrom, overcoatingthe dried, uncured first coating with the second extended prepolymersolution, thereby to cause diffusion of at least a portion of saidsecond prepolymer solution into the dried uncured first coating, drivingoff the solvent, and curing the resulting membranous coating.

The cured non-porous polyurethane membranes of the invention may beprepared separate and apart from the porous substrate over which theymay ultimately be disposed, such as by forming of the uncured membraneon a release surface followed by curing thereof. Moreover, the membranesof the invention can be disposed over a porous substrate to render samewaterproof and water vapor tranmissive in any suitable manner, such asby discontinuously securing the membrane to the substrate surface usingmechanical securing elements. However, it is much preferred that themembrane be continuously bonded to the substrate surface, and this cangenerally be achieved by a direct solution coating technique such asoutlined above and/or by adhering the membrane to the substrate surfaceby means of a compatible continuous water vapor transmissible adhesiveinterposed between the substrate surface and the membrane of theinvention.

Many porous articles, such as woven and non-woven fabrics, natural andporomeric artificial leathers, papers and ceramics can be renderedwaterproof and water vapor tranmissible by disposition of the membranesof the invention thereover. The direct solution coating and continuousadhesive techniques mentioned above are particularly amenable to thepreparation of waterproof and water vapor transmissible fabrics andfabric laminates utilizing the membranes of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Utilizing the preferred prepolymer route for preparing the polyurethanemembranes of the invention, the prepolymers are produced in accordancewith conventional methodology whereby the polyols and reactivepolydimethylsiloxane are reacted with a stoichiometric excess of thepolyisocyanate and the resulting isocyanate terminated prepolymer isthen reacted with a relatively low molecular weight difunctional chainextender.

Polyalkylene ether glycols generally suitable for preparation of theprepolymers of the invention are those known in the polyurethanepreparative art. The polyalkylene ether glycols of interest aregenerally those prepared from ethylene oxide (polyoxyethylene glycol),propylene oxide (polyoxypropylene glycol), butylene oxide(polyoxybutylene glycol), copolymers and mixtures thereof and preferablyhave average molecular weights of between about 450 and 2000 since suchglycols are either liquids at room temperature or may be readilyliquified by mild heating thereof. I generally prefer that the startingmaterial polyalkylene ether glycols employed be difunctional, that is tosay having a functionality of 2. Where a prepolymer of the invention isprepared from polyalkylene ether glycols have functionalities ofsubstantially greater than 2, for instance 2.2 or greater, the resultingpolyurethane prepolymers tend to be excessively branched, thereby toexhibit viscosities which are excessive for further polymer preparationand handling.

It is known that non-porous hydrophilic breathable polyurethane coatingsand membranes can be produced utilizing polyoxyethylene glycols as theprimary polyol. However, hydrophilic polyurethanes whose backbones arecomposed entirely or nearly entirely of ethylene oxide units tend toswell greatly upon contact with water and the wet physical properties ofsuch polyurethanes are generally wholly inadequate for practical use asmembranous breathable waterproofing materials. In the present invention,the polyalkylene ether glycol(s) used in combination with thepoly(oxyethylene) glycol, that is to say, those polyalkylene etherglycols wherein the number of carbon atoms of the alkylene radical is atleast 3, serve to confer sufficient wet strength properties to the curedpolyurethane composition as to permit the practical use thereof in theform of a breathable waterproofing membrane. In order to assure thisresult, the molar ratio of the poly(oxyethylene) glycol to the otherpolyalkylene ether glycols in the compositions of the present inventionshould be within the range of 1.5:0.5 to 0.5:1.5 and is preferably about1:1. In general, it can be said that, all other factors being equal, thehigher the molar ratio of the poly(oxyethylene) glycol component to theother polyalkylene ether glycol(s) in the composition, the greater thewater vapor transmission properties and the lower the wet physicalproperties in a cured membrane prepared therewith. Conversely, the lowerthe molar ratio of the poly(oxyethylene) glycol component to the otherpolyalkylene ether glycols in the composition, the lesser the watervapor transmission properties and the higher the wet physical propertiesin a cured membrane prepared therewith. Indeed, based on the relativelyhigh concentration of the polyalkylene ether glycol component whosealkylene groups comprise at least 3 carbon atoms in the compositions ofthe invention, it would be predicted that the water vapor transmissionrates attainable in cured membranes prepared therewith would be too lowfor practical utility, particularly in such textile applications asrainwear fabrics where a moisture (or water) vapor transmission rate asdetermined by the Upright Cup Test Method of ASTM-E96-B 66B, hereinafterreferred to as "MVTR", of at least 500 gms/m² /24 hours is considerednecessary for maintaining the comfort of a wearer of a garmentmanufactured from the fabric. In the membrane compositions of theinvention the attainment of MVTR values of at least 500 gms/m² /24 hoursand substantially higher in the cured membrane is markedly facilitated,despite the relatively high concentration of the C₃ and higherpolyalkylene ether glycol component, by the additional presence of arelatively minor proportion of a reactive polydimethylsiloxane componentwhich apparently forms a hydrophobic, water vapor transmissive block inthe polymer backbone of the cured composition.

The reactive polydimethylsiloxane starting materials of interest arethose which comprise a linear or lightly branched polydimethylsiloxanebackbone and which further comprise at least two reactive, usuallyterminal, hydroxyl groups per molecule, that is to say, a functionalityof at least 2. Such reactive polydimethylsiloxanes are commerciallyavailable in various average molecular weight fractions from suchsources as Dow Chemical Company, Midland, Mich. and General ElectricCompany, Silicones Division, Schenectady, N.Y. In general, I prefer thatthe average molecular weight of the reactive polydimethylsiloxaneutilized as a starting material in the preparation of the polyurethanecompositions of the invention reside within the range of from 800 to3500. As previously mentioned, the mole ratio of the reactivepolydimethylsiloxane to the total polyalkylene ether glycol content ofthe final composition should be within the range of 0.1:1 to 0.3:1.Generally speaking, all other factors being equal, the higher the moleratio of the reactive polydimethylsiloxane within the foregoing rangethe greater will be the MVTR values attainable in the cured polyurethanemembranes prepared therewith.

Polyisocyanates useful in the preparation of the polyurethanecompositions of the invention generally include any of the diisocyanatesconventionally employed in the preparation of polyurethanes. Exemplaryof these are: toluene diisocyanate, diphenylmethane diisocyanate,napththalene diisocyanate, isophorone diisocyanate, dicyclohexylmethanediisocyanate, dimethoxydiphenyl diisocyanate, p-xylene diisocyanate,hexamethylene diisocyanate, tetramethylxylene diisocyanate and the like.Where the preferred prepolymer route is employed, and as is knownpractice in the preparation of polyurethane prepolymers, the quantity ofthe polyisocyanate employed in preparing the prepolymer is instoichiometric excess relative to the reactive hydroxyl group populationof the polyalkylene ether glycol and reactive polydimethylsiloxanecomponents, thereby to ensure that the resulting prepolymermacromolecular product will be terminated with reactive --NCO groups.Thus, the quantity of the polyisocyanate employed in the preparation ofthe prepolymers of the invention will be sufficient to provide at least100% of the --NCO groups necessary to react with the hydroxyl groups ofthe polyalkylene ether glycols and reactive polydimethylsiloxanecomponents of the prepolymer reaction mixture. As a matter ofconvenience, the amount of polyisocyanate introduced to the polyalkyleneether glycol and polydimethylsiloxane components can be sufficiently inexcess to handle the needs of the subsequent chain extension of theprepolymer wherein a relatively low molecular weight bifunctional chainextender is incorporated in and reacted with the NCO- terminatedprepolymer.

Suitable chain extenders are well known in the polyurethane preparativeart and generally comprise organic molecules having a molecular weightsof between 200 and 600 and having two terminal groups comprising labilehydrogen atoms, such as hydroxyl or amino groups. Glycols, diamines,alkanolamines and hydroxy acylamines are typical classes of such chainextenders. Specific examples are: 1,4-butanediol, phenylene diamine,ethanolamine, ethylene diamine, butane diamine, 1,4-cyclohexanedimethanol, bis(hydroxyethyl)bisphenol A, bis(2-hydroxyethyl)carbamateand the like.

In addition to the foregoing components, the polyurethane compositionsof the invention may also have incorporated therein various additivesand modifiers conventional in the polyurethane formulation art. Suchadditives and modifiers may take the form of curatives, pigments,colorants, antiblocking agents, antioxidants, catalysts, flattingagents, anticurling agents and the like. Where the prepolymer route isemployed such additives and modifiers other than catalysts are usuallyincorporated into the polymer system only after chain extension of theprepolymer has been achieved.

The viscosity of the prepolymers of the invention and of the chainextended products thereof can range from that of a water thin liquid tothe consistency of a thick, slow pouring grease or semi-solid. Generallyspeaking, in those instances wherein the prepolymer or chain extendedpolymer viscosity is likely to become excessive for subsequentoperations, such as for chain extension of the prepolymer or forutilization of the chain extended polymer product in conventionaltextile coating techniques, such as by spraying, doctor blading, rollcoating and the like, the viscosity of the prepolymer or the chainextended polymer can be readily reduced to an acceptable level bydissolution of the prepolymer or polymer in one or more suitablesolvents. Indeed, as is demonstrated in certain of the working exampleshereof, the viscosities of the prepolymer and chain extended polymersystems can be controlled by addition of suitable inert organic solventsto the prepolymer subsequent to its formation and by carrying out theprepolymer chain extension polymerization step in the presence ofsuitable inert organic solvents.

Where the membranes of the invention are to be applied to a fabricsurface utilizing a solvent coating technique without lamination of thecoated fabric to another fabric, it can be desirable to afford physicalprotection of the exposed surface of the solvent coated waterproof andwater vapor transmissible polyurethane membrane by overcoating theexposed surface thereof with a protective water vapor transmissiblepolyurethane topcoat composition. Said topcoat composition may also beapplied by a solvent coating technique to the dried, but uncured,membrane, the solvent driven off from the topcoat and the resultingcomposite coating cured. Where a first fabric layer is to be laminatedto a second fabric layer with the cured waterproof and water vaportransmissible membrane of the invention interposed therebetweeen, thefirst of the fabric layers can be first directly coated with a precursormembrane solution comprising a chain extended polyurethane prepolymerprepared from the poly(oxyethylene) glycol and reactivepolydimethylsiloxane components and the solvent driven off from this asyet compositionally incomplete coating. Then, a coating solutioncontaining a water vapor transmissible chain extended polyurethaneadhesive solute which also contains the polyalkylene ether glycolcomponent required to complete the membrane coating is overcoated ontothe precursor membrane coating and the solvent driven off therefrom.Next, the second fabric layer is brought into contact with the coatedadhesive of the first fabric layer under sufficient pressure as toestablish the fabric laminate structure and to cause sufficientintermingling the adhesive coating into the precursor membrane coatingso as to establish in the membrane coating the compositionalrequirements of the invention.

There follow a number of illustrative non-limiting examples.

EXAMPLE 1 Preparation of Basecoat Formulation Urethane Chain ExtendedPrepolymer

The following ingredients are employed, in the stated weightpercentages.

    ______________________________________                                        Ingredient               Weight Percent                                       ______________________________________                                        Isophorone diisocyanate (IPDI)                                                                         15.786                                               CARBOWAX 1450, a poly(oxyethylene) glycol                                                              46.690                                               having an average molecular weight of 1450                                    and a functionality of 2 (Union Carbide                                       Corp., Danbury, CT)                                                           Silicone Q4-3667, a polydimethylsiloxane                                                               7.762                                                having functional hydroxyl groups, and a                                      functionality of about 2 (Dow Chemical                                        Company, Midland, MI)                                                         COSCAT 83, a catalyst (Cosan Chemical                                                                  0.024                                                Company, Carlstadt, NJ)                                                       Toluol                   29.738                                               ______________________________________                                    

The apparatus employed to prepare the prepolymer is an assiduouslypredried reaction kettle equipped with heating and stirring means. Atabout room temperature the IPDI is first charged into the kettle and,with constant stirring, there are then slowly added at proportionaterates the poly(oxyethylene) glycol and polydimethylsiloxane. Since thepoly(oxyethylene) glycol employed is a solid at room temperature it isheated to melting and charged into the kettle in the liquid state. Therelative quantities of these ingredients provides a reaction mixturehaving a stochiometric excess of IPDI, the NCO:OH ratio thereof beingabout 2:1. Upon completion of the addition of the poly(oxyethylene)glycol and polydimethylsiloxane, the kettle is heated to and maintainedat a temperature of 160°-180° F. Upon attainment of this goaltemperature the catalyst is added and the resulting reaction mixturestirred for a period of between about 4 and 6 hours. Next, the toluol isadded and stirred into the prepolymer product of reaction and the kettlecooled to below about 100° F. The reaction product is sampled and testedfor free NCO and is found to have a free NCO content of about 3%, byweight. Upon analysis of the polymeric reaction product it is found thatit comprises an isocyanate capped copolymer polyurethane having randompolyethylene oxide and polymethyldisiloxane blocks. The prepolymer isthen chain extended as follows.

Chain Extension of Prepolymer

The following ingredients are employed, in the stated weightpercentages.

    ______________________________________                                        Ingredient           Weight Percent                                           ______________________________________                                        Prepolymer solution  52.025                                                   Toluol               11.653                                                   Methyl ethyl ketone  12.741                                                   Isopropyl alcohol    11.653                                                   Chain Extender (20 wt. % solution                                                                  11.928                                                   of isophorone diamine in toluol)                                              (IPD Solution)                                                                ______________________________________                                    

The prepolymer mixture is charged into an assiduously predried,moisture-free stirred reaction kettle maintained at about roomtemperature. Next, the toluol, methyl ethyl ketone and isopropyl alcoholsolvents are stirred into the prepolymer mixture in order to provide areaction mixture having a water thin viscosity and a 35-40 wt. %prepolymer solids content. Next, the chain extender solution is trickledinto the water thin reaction mixture with agitation. Over the period ofthe chain extender addition the viscosity of the mixture increases tobetween about 100,000 and 110,000 cps at 25° C. as measured with aBrookfield Viscometer using a #6 spindle at 20 revolutions per minute.

EXAMPLE 2 Preparation of Basecoat Formulation Urethane Chain ExtendedPrepolymer

In a stirred reaction kettle of the type utilized and in the generalmanner disclosed in Example 1, a prepolymer is prepared utilizing thefollowing ingredients, in the stated weight percentages.

    ______________________________________                                        Ingredient               Weight Percent                                       ______________________________________                                        CARBOWAX 1450            23.335                                               TERATHANE 2000, a polytetramethylene ether                                                             32.659                                               glycol having an average molecular weight of                                  2000 and a functionality of 2 (E.I. du Pont                                   de Nemours, Inc., Wilmington, DE)                                             Isophorone diisocyanate (IPDI)                                                                         12.096                                               COSCAT 83                 0.024                                               Toluol                   31.886                                               ______________________________________                                    

The prepolymer reaction mixture is heated and stirred at a temperaturewithin the range of from about 165° F. to about 180° F. for a period ofabout 4 hours, followed by addition of the toluol solvent and cooling ofthe resulting prepolymer solution to below about 100° F. Said prepolymersolution has a free NCO content of 1.42 wt. %.

Chain Extension of Prepolymer

The prepolymer of this Example is chain extended in a manner similar tothat of Example 1 utilizing the following ingredients, in the statedweight percentages.

    ______________________________________                                        Ingredient          Weight Percent                                            ______________________________________                                        Prepolymer solution 56.457                                                    Methyl ethyl ketone 12.340                                                    Toluol              13.266                                                    Isopropyl alcohol   12.168                                                    Chain extender (IPD solution)                                                                      5.767                                                    ______________________________________                                    

Upon completion of the trickled addition of the chain extender theresulting chain extended polymer solution has a Brookfield viscosity ofbetween 100,000 and 110,000 cps at 25° C.

EXAMPLE 3 Preparation of Thermosettable Breathable Basecoat CoatingFormulation Suitable for Direct Coating of Fabrics

Into a stirred kettle are mixed the following ingredients, in the statedweight percentages.

    ______________________________________                                        Ingredient              Weight Percent                                        ______________________________________                                        Chain extended polyurethane solution                                                                  65.020                                                of Example 2                                                                  Chain extended polyurethane solution                                                                  27.821                                                of Example 1                                                                  SANTOLITE MHP, an anti-curl additive                                                                  2.128                                                 (Monsanto Co., St. Louis, MO)                                                 CYMEL 380, a melamine anti-blocking                                                                   3.179                                                 agent (American Cyanamid, Inc., Bridgeport,                                   CN)                                                                           20 wt. % solution of a triethylamine                                                                  1.852                                                 blocked ethyl acid phosphate catalyst                                         dissolved in toluol                                                           ______________________________________                                    

This formulation, once it has been completed by incorporation of theacid catalyst therein, is in the nature of a promoted resin systemwhich, upon long standing, ultimately thickens and gels. Accordingly, atleast for direct coating applications, once the acid catalyst has beenadded the completed formulation should normally be utilized within about24 hours of its preparation. The mole ratio of poly(oxyethylene) glycol(derived from the chain extended prepolymer of Example 1) topolytetramethylene ether glycol (derived from the chain extendedprepolymer of Example 2) contained in this formulation is 1:1. The moleratio cf the polydimethylsiloxane constituent (derived from theprepolymer of Example 1) to the total glycols (derived from theprepolymers of Examples 1 and 2) contained in the formulation is 0.1:1.

EXAMPLE 4 Preparation of Thermosettable Breathable Basecoat CoatingFormulation Suitable for the Preparation of Laminated Fabrics

The following ingredients, in the stated weight percentages. are stirredin a kettle at room temperature until uniformly mixed.

    ______________________________________                                                                WEIGHT                                                INGREDIENT              PERCENT                                               ______________________________________                                        Chain extended prepolymer solution of                                                                 95.00                                                 Example 1                                                                     CYMEL 380 melamine anti-blocking agent                                                                4.00                                                  Catalyst solution consisting of 40 wt. %                                                              1.00                                                  ethyl acid phosphate dissolved in toluol                                      ______________________________________                                    

The resulting basecoat formulation has a Brookfield viscosity of between30,000 and 35,000 cps at 25° F.

EXAMPLE 5 Preparation of Thermosettable Breathable Topcoat FormulationSuitable for Topcoating of Dried Basecoat of Example 3

This formulation comprises a blend of polyester and polyether chainextended urethane prepolymer solutions each of which is prepared in amanner similar to that described in previous examples. The first chainextended urethane prepolymer solution is prepared utilizing thefollowing ingredients, in the stated weight percentages.

9337 Preparation of First Urethane Prepolymer Solution

    ______________________________________                                        PREPOLYMER (1)                                                                INGREDIENT          WEIGHT PERCENT                                            ______________________________________                                        MILLESTER VII-110, 1,4 Butandiol                                                                  50.099                                                    adipate (Polyurethane Specialties                                             Co., Inc., Lyndhurst, NJ)                                                     Isophorone diisocyanate                                                                           20.291                                                    COSCAT 83           .001173                                                   Butylated Hydroxy Toluene                                                                         .002346                                                   Toluol              29.573                                                    ______________________________________                                    

The reaction mixture, minus the toluol, is heated and stirred overnightat about 160° F. The mixture is cooled to below about 100° F. and thetoluol then mixed thereinto to form a prepolymer solution.

Chain Extension of First Urethane Prepolymer

The above prepolymer solution is chain extended by addition thereto ofthe following ingredients, in the stated weight percentages.

    ______________________________________                                        CHAIN EXTENDED PREPOLYMER (I)                                                 INGREDIENT        WEIGHT PERCENT                                              ______________________________________                                        Prepolymer solution (1)                                                                         39.858                                                      Toluol            21.166                                                      Isopropyl alcohol 28.239                                                      IPD chain extender solution                                                                     10.737                                                      ______________________________________                                    

As previously, the chain extender solution is trickled into the systemonly after the addition and admixture of the toluol and isopropylalcohol solvents therein. The resulting chain extended polymer solutionhas a Brookfield viscosity within the range of 45,000-60,000 cps at 25°F. The chain extension reaction is then shortstopped or terminated withmorpholine.

The second urethane prepolymer solution is prepared utilizing thefollowing ingredients, in the stated weight percentages.

Preparation of Second Urethane Prepolymer Solution

    ______________________________________                                        PREPOLYMER (2)                                                                INGREDIENT            WEIGHT PERCENT                                          ______________________________________                                        CARBOWAX 1000, a poly(oxyethylene)                                                                  48.467                                                  glycol having an average molecular                                            weight of about 1000                                                          Isophorone diisocyanate                                                                             21.483                                                  COSCAT 83             .001189                                                 Toluol                30.038                                                  ______________________________________                                    

The reaction mixture, minus the toluol solvent, is heated and stirredfor 3 to 4 hours at a temperature of about 180° F. Thereafter, themixture is cooled to below about 100° F. and the toluol mixed thereinto.

Chain Extension of Second Prepolymer

Chain extension of the second prepolymer is achieved using the followingingredients, in the stated weight percentages.

    ______________________________________                                        CHAIN EXTENDED PREPOLYMER (2)                                                 INGREDIENT          WEIGHT PERCENT                                            ______________________________________                                        Prepolymer solution (2)                                                                           45.700                                                    Toluol              20.259                                                    Isopropyl alcohol   19.415                                                    20 wt. % IPD chain extender solution                                                              14.626                                                    ______________________________________                                    

As previously, the IPD chain extender solution was trickled into thestirred formulation only after addition and admixing of the toluol andisopropyl alcohol solvents thereinto. The resulting chain extendedprepolymer solution was then shortstopped with morpholine.

Preparation of Topcoat Formulation

The final topcoat formulation is prepared by admixing the foregoingprepolymer solutions along with additional ingredients. The ingredientsof the topcoat formulation are given below in their order of mixing,along with the weight percentages thereof.

    ______________________________________                                        TOPCOAT FORMULATION                                                           INGREDIENT            WEIGHT PERCENT                                          ______________________________________                                        Chain Extended Prepolymer solution (1)                                                              36.819                                                  Isopropyl alcohol     12.269                                                  Toluol                5.724                                                   CAB 381-0.5, a cellulose acetate butyrate                                                           2.935                                                   film hardener (Eastman Chemicals,                                             Kingsport, TN)                                                                Chain Extended Prepolymer solution (2)                                                              37.731                                                  AEROSIL TS100, a hydrophobic                                                                        2.525                                                   pyrogenic silica flatting agent (Degussa,                                     Inc., Ridgefield Park, NJ)                                                    50 wt. % solution of petrolatum in toluol                                                           .396                                                    CYMEL 303 melamine anti-blocking                                                                    1.071                                                   agent                                                                         Catalyst solution consisting of 45 parts                                                            .529                                                    by weight of Catalyst 4040, a p-toluene                                       sulfonic acid solution (American                                              Cyanamid, Inc.) reduced in 55 parts                                           by weight isopropyl alcohol                                                   ______________________________________                                    

This topcoating formulation has a Brookfield viscosity at 25° F. ofbetween 10,000 and 15,000 cps.

EXAMPLE 6 Preparation of Breathable Thermosettable Polyurethane AdhesiveSuitable for Bonding of Membrane Composed of Dried Basecoat of Example 4to a Fabric

Into a dry reaction kettle equipped with stirring, heating and coolingmeans there are charged the following ingredients, in the statedweights:

    ______________________________________                                                                 WEIGHT                                               INGREDIENT               (LBS)                                                ______________________________________                                        TERATHANE 2000, polytetramethylene ether                                                               23.037                                               glycol                                                                        MODUR M, methylene diisocyanate                                                                         5.799                                               (Miles, Inc., Pittsburg, PA))                                                 Stabilized 1,1,1-trichloroethane                                                                       14.022                                               ______________________________________                                    

These ingredients are heated to about 110° F., with constant mixing, forabout 1/2 hour at which time the heating means of the kettle isdeactivated. Then, 15.024 lbs of M-Pyrol solvent (GAF Chemicals Corp.,Wayne, N.J.) and 0.010 lb of Fomrez C-2 tin based catalyst (WitcoChemical Corp., Chicago, Ill.) are charged into the kettle and thecooling means activated to maintain the temperature of the contents atbetween 115° and 120° F. for about one hour. Then, there are added tothe reaction mixture 16.026 lbs of stabilized 1,1,1-trichloroethane and1.042 lbs of 1,4-butanediol chain extender with constant mixing andmaintenance of the resulting reaction mixture at a temperature ofbetween 115° and 125° F. The Brookfield viscosity of the mixture ismonitored and, upon attainment of a viscosity (at the reactiontemperature) of about 80,000 cps, there is charged thereinto anadditional 25.040 lbs of stabilized 1,1,1-trichloroethane and, uponcompletion of its admixture, the chain extension reaction is thenterminated or shortstopped with methanol. The viscosity of thispolyurethane solution at 25° F. is between about 100,000 and about120,000 cps. The viscosity is reduced to about 40,000 cps by mixing thepolymer solution with additional 1,1,1-trichloroethane in an 85:15weight ratio, thereby to provide an unpromoted polyurethane adhesiveformulation which, prior to use, must be admixed with a sufficiency of apolyisocyanate having a functionality of at least three in order topromote cross linking thereof.

EXAMPLE 7 Direct Coating of Fabric

Coating is achieved by a multiple serial doctor blading stationapparatus comprising an elongate flat trough bed to support a textilepassed therethrough and having feed and take-off ends. Preceding thefeed end of the trough is a feed reel to feed a textile to be coatedinto the feed end of the trough. Positioned above the trough at spacedapart locations along the length thereof are three doctor bladestations, each comprising a liquid coating delivery system by which todeliver liquid coating material to the upper surface of a textilerunning through the trough followed by an adjustable doctor bladerunning across the width of the trough. Following each doctor bladestation is a solvent flashing and vapor recovery station. Immediatelyfollowing the take-off end of the doctor blading apparatus is athermostatically controlled curing oven having feed and take-off ends,said oven being adapted to receive into the feed end thereof a coatedtextile from the take-off end of the doctor blading apparatus and todischarge the cured coated textile to a take-up reel located downstreamtherefrom.

A bolt of tightly woven 3 ounce/yd.² nylon cloth having a thickness ofabout 8 mils is treated utilizing the above-described apparatus. Thebasecoat formulation of Example 3 is fed to the first and second doctorblading stations, the doctor blades thereof each being set at a spacingof 2-3 mils above the cloth surface. The delivery rate of the basecoatcoating formulation to each of the doctor blading stations is metered toprovide a coating weight of between 1 and 1.5 ounces basecoat/yd² ofcloth. The topcoat formulation of Example 5 is fed to the third doctorblading station, the doctor blade of this station being set to a spacingof 2-3 mils above the basecoat coated cloth surface and the rate ofdelivery of the topcoat formulation being metered to provide a coatingweight of between 1 and 1.5 ounces of the topcoat formulation/yd² ofcloth. After passing through the last of the solvent flashing andrecovery stations the thusly multiply coated cloth is passed through thecuring oven maintained at a temperature of about 325° F., the residencetime of the cloth therein being controlled by the take-up reel tobetween 1 and 2 minutes. After passing from the curing oven and, priorto being taken up on the take-up reel, the bottom or uncoated side ofthe cloth is treated with a water repelling fluorocarbon compositionsuch as that marketed under the brand name ZEPEL (E.I. du Pont deNemours & Company, Wilmington, Del.).

Upon visual inspection, the cured polyurethane coating is noted to besmooth, uniform and devoid of structural defects. Attempts to strip thecoating from the cloth reveal that the coating is strongly adherent tothe nylon fabric substrate, the mode of failure, when achieved at all,tending to be in the nature of failure in cohesion rather than adhesion.Specimens of the coated cloth are subjected to waterproofness andmoisture vapor transmission tests. Waterproofness is assessed by use ofthe Mullin's Burst Test (Fed. Std. 191, Method 5512) and failure of thecoated textile occurs at an average hydrostatic pressure of about 120p.s.i. Moisture vapor transmission rate is determined by the Upright CupTest Method of ASTM-E96-66B and is found to be within the range of500-600 gms/m² /24 hours. However, the upright cup method ofASTM-E96-66B is considered by those of skill in the art to be deficientin determining high range moisture vapor transmission rates due, inlarge part, to the fact that the test inherently places an interferingair gap between the bulk water contained in the upright cup and the testmaterial sealed to the mouth of the cup. Moreover, where the specimen isa fabric believed to have utility in applications wherein direct contactthereof with bulk water is anticipated, the Upright Cup method does notsimulate such a direct wetting condition. Accordingly, it isconventional practice to test specimens believed to possess high watervapor transmission rate capabilities by means of a modified test whereinthe specimen is sealed to the mouth of the upright cup containing thecharge of water and the cup then inverted in order to avoid altogetherthe air gap between specimen and water charge and to thereby place thebulk water in direct contact with the specimen material. The coatedtextile of this example is also tested by this inverted cup modificationof the ASTM-E96-66B method and the moisture vapor transmission ratethereof is found to be within the range of 6000 to 7000 gms/m² /24hours. In handling of the coated textile it is noted that the hand andstiffness thereof is little changed, if at all, from that of theuncoated cloth. From the foregoing results, it is apparent that thecoated textile of the present example would make an excellent shellmaterial for waterproof garments or other waterproof textileapplications wherein water vapor transmissibility, as well aswaterproofness, are essential or desirable traits.

EXAMPLE 8 Preparation of Fabric Laminate Comprising BreathableWaterproof Basecoat Sandwiched Between Fabric Layers

A doctor blading line similar to that employed in the previous exampleis utilized. However, interposed between the take-off end of the doctorblading trough and the curing oven are a nip roll and, in oppositionthereto, a calendering roll equipped with pressure adjustment means bywhich to adjust the pressure of the one roll against the other. Inaddition, a second feed reel is stationed upstream of the calender andnip rolls, thereby to provide means by which a second cloth may beapplied to the coated cloth entering the calender and nip rolls.

The textiles employed in this example are each a tightly woven 3 oz/yd²nylon cloth. The cloth fed by the first feed reel through the coatingline is coated at the first station and recoated at the second stationwith the basecoat polyurethane formulation of Example 4, the coatingdelivery rates at each station being metered at 0.4 to 0.5 oz/yd². Atthe third coating station the basecoat coated cloth is overcoated withthe adhesive formulation of Example 6 which has been freshly promoted byadmixture thereof with 3 parts by weight/100 parts of the adhesivesolution of a crosslinker polyisocyanate such as MONDUR CB-75 (Miles,Inc., Pittsburgh, Pa.) or its equivalent. The promoted adhesiveformulation is delivered to the basecoated cloth at a rate of about 0.3oz/yd² and is doctor bladed at the third coating station to a thicknessof about 2 wet mils. After passing the third solvent flashing station,the second cloth from the second feed roll is applied to the adhesivelycoated upper surface of the first textile and both are passed throughthe nip of the opposed nip and calender rolls under a roll pressure ofseveral tons, thereby to effect continuous laminating contact of thesecond cloth to the adhesively coated surface of the first cloth and,further, to cause sufficient intermingling of the polytetramethyleneether glycol based adhesive formulation with the poly(oxyethylene)glycol and reactive polydimethysiloxane based basecoat formulation suchthat an intermediate composition falling within the compositionalparameters of the invention is formed therebetween. The resulting clothlaminate is then passed through the curing oven held at a temperature ofabout 350° F. and at a residence time of between about 1 and 2 minutes.

Specimens of the cloth laminate are tested for waterproofness andmoisture vapor transmission rate (MVTR) in accordance with the Mullin'sBurst Test Procedure of Federal Standard 191, Method 5512 andASTM-E96-66B, respectively. The average burst strength is determined tobe 150 p.s.i. and the average MVTR is determined to be 500 gms/m² /24hours. On the bases of these waterproofness and MVTR values, thelaminated cloth product of this example is assessed as suitable for useas a material of construction of rain protective garments and in othertextile applications wherein the qualities of waterproofness and watervapor transmissibility are necessary or desirable.

The foregoing description and examples are illustrative in character anddemonstrate certain embodiments and techniques for implementation anduse of the present invention. It should be recognized and understood,however, that said description and examples are not to be construed aslimiting of the invention because many changes, modifications andvariations may be made therein without departing from the scope, spiritor intention of the invention, as will be obvious to those skilled inthe art.

What is claimed is:
 1. A method for fabricating a waterproof, watervapor transmissible fabric laminate which comprises:A) providing a pairof fabric layer elements; B) applying a basecoat coating onto a face ofone of said fabric layer elements, said basecoat being a membraneprecursor composition comprising a chain extended polyurethaneprepolymer composition, said composition being a block copolymerreaction product of: (a) a polyisocyanate; (b) a polyalkylene etherglycol wherein the number of carbon atoms of the alkylene radicalthereof is 2; and (c) an isocyanate reactive hydroxyl group-containingpolydimethylsiloxane having a functionality of at least 2; C) applying awater vapor transmissible adhesive overcoat coating onto the basecoatprecursor membrane coating, said adhesive overcoat comprising a chainextended polyurethane prepolymer composition, said composition being thereaction product of (a) a polyisocyanate and (b) a polyalkylene etherglycol wherein the number of carbon atoms of the alkylene radicalthereof is at least 3; D) contacting a face of the second fabric layerwith the coated face of said first fabric layer under sufficientpressure to cause intermingling of the adhesive coating with thebasecoat precursor membrane coating and to thereby provide therebetweenan intermingled chain extended prepolymer membrane wherein the moleratio of the polyalkylene ether glycol of (B)(b) to the polyalkyleneether glycol of (C)(b) is within the range of from 1.5:0.5 and 0.5:1.5and the mole ratio of said polydimethylsiloxane of (B)(c) to the totalof said polyalkylene ether glycols of (B)(b) and (C)(b) is within therange of from 0.1:1 to 0.3:1; and (E) curing the prepolymer compositionsinterposed between said fabric layers.
 2. The method of claim 1 whereineach of said polyalkylene ether glycols of (B)(b) and (C)(b) has anaverage molecular weight of between about 450 and about
 2000. 3. Themethod of claim 1 wherein said polydimethylsiloxane of (B)(c) has anaverage molecular weight of between about 800 and about
 3500. 4. Themethod of claim 1 wherein at least one of said fabric layers is a wovenfabric.
 5. The method of claim 4 wherein said at least one fabric layeris composed of nylon.
 6. The method of claim 1 wherein at least one ofsaid fabric layers is a non-woven fabric.
 7. The method of claim 1wherein each of said polyalkylene ether glycols of (B)(b) and (C)(b) hasa functionality of
 2. 8. The method of claim 1 wherein said basecoatprecursor membrane coating and said adhesive overcoat coating are eachapplied in the form of a solution thereof in a fugitive solventcomponent and wherein following application of each said coating saidfugitive solvent component is removed therefrom.
 9. The method of claim8 wherein said basecoat precursor membrane coating is applied at leasttwice to said first fabric layer prior to applying said adhesiveovercoat coating thereonto.